From the earliest days of the COVID-19 pandemic, people have commonly experienced brain fog after having COVID-19. Years after the pandemic, mounting research reveals that COVID-19 long-term side effects go far beyond just respiratory issues. Abundant evidence suggests COVID-19 affects the brain and impairs neurocognitive ability. Those with “brain fog” say they experience sluggishness, struggling with memory retention and difficulty concentrating.
Studies now link SARS-CoV-2 infection to measurable cognitive declines, including reduced IQ scores, persistent brain fog, and structural changes in the brain. Studies have observed this even among those who experienced mild initial infections. On top of brain fog, COVID-19 can lead to headaches, strokes and sleep problems. COVID-19 has also been known to cause an array of other problems, including several mental health issues.
A Cognitive Crisis
A 2024 New England Journal of Medicine study of over 113,000 individuals revealed measurable cognitive deficits linked to COVID-19 long-term side effects, even in mild cases. Participants who recovered from mild infections showed a 3-point IQ decline, while those with unresolved long COVID symptoms experienced a 6-point drop.
Hospitalized patients, especially ICU admissions, faced a 9-point IQ loss, with reinfection adding an extra 2-point deficit. These cognitive deficits affect memory, reasoning, and executive function. These changes in the brain were noted to mirror cognitive aging equivalent to 20 years.
Imaging studies observed structural brain changes, including reduced gray matter volume and brain tissue damage. Notably, early variants like the original strain and Alpha caused larger impacts than Omicron. Even those whose symptoms resolved within weeks showed persistent, although smaller, cognitive impairments, demonstrating the pervasive nature of COVID-19 long-term side effects.
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How COVID-19 Harms the Brain
Recent research confirms that COVID-19 long-term side effects on the brain involve a mix of biological and structural changes that can persist well after the initial infection. Large population studies show that people who have had COVID-19 face a higher risk of memory problems and cognitive decline than those who have not been infected.
Imaging studies using advanced MRI techniques have found that even mild COVID-19 can result in measurable shrinkage of brain volume. It especially causes shrinkage in the frontal and parietal lobes and the right thalamus. These regions are responsible for memory and reasoning. The extent of this shrinkage increases with illness severity, and those with more severe cases show greater brain volume loss compared to healthy controls.
Simultaneously, persistent inflammation in the brain, triggered by the body’s immune response, disrupts normal brain cell communication and repair. This further exacerbates cognitive difficulties. This inflammation can also break down the blood-brain barrier, allowing harmful substances to enter the brain and worsen damage.
In some cases, autopsies detected SARS-CoV-2 still present in brain tissue. Laboratory studies on both human and mouse brains show that SARS-CoV-2 can cause brain cells to fuse together.. This effectively acts as a short-circuit to the brain by disrupting regular brain electrical activity, impairing function.
Volume loss, inflammation, barrier breakdown, and direct viral effects impacting the brain explain why many people experience memory loss amongst an array of cognitive issues after COVID-19, even if their initial symptoms were mild. Researchers pooled data from 11 different studies. They studied almost a million people with COVID-19 and more than 6 million uninfected individuals. They found that people over 60 who had COVID-19 were more likely to receive a new onset dementia diagnosis than those who never had the virus.
Long COVID’s Persistent Shadow
A University of Miami study tracked patients who had recovered from COVID-19 for over 2 years and found that many continued to struggle with persistent cognitive issues, including brain fog, memory lapses, and slowed processing speed. These symptoms were not limited to those with severe initial infections. Individuals who experienced mild or moderate COVID-19 reported continuous difficulties with word-finding, memory retention and recall and overall mental clarity.
These findings suggest that COVID-19 long-term side effects can stay well beyond the acute phase of illness. Similarly, a European study reported that a year after infection, 59% of patients described persisting symptoms such as fatigue and concentration difficulties, while 64% showed abnormal neurological findings during clinical exams.
Importantly, research also indicates that these COVID-19 long-term side effects disproportionately impact marginalized communities, including Hispanic and Black populations, who already face higher rates of neurocognitive disorders and systemic health disparities. As research continues to grow on COVID-19 long-term side effects, it is clear that it can leave a lasting imprint on cognitive function, regardless of the severity of the initial infection.
Conclusion
The growing evidence is clear that COVID-19 can leave lasting cognitive scars. Regardless of initial infection severity, COVID-19 can cause neurodegenerative issues such brain fog to measurable declines in memory and reasoning. Ongoing research is vital to understand and address these long-term effects, especially for vulnerable populations, and to develop effective treatments for this new cognitive crisis.
Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.
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